Fuel injection systems

ABSTRACT

This invention relates to a fuel injection system and to a fuel pressure regulator therefor. A fuel injection system, for injecting pressurised fuel into an inlet duct or manifold of an engine includes a fuel-flow metering orifice which is fed with the pressurised fuel and which is exposed on its downstream side to the pressure obtaining in the inlet duct or manifold, and a fuel pressure regulator is arranged to regulate the fuel to a pressure which exceeds the inlet duct pressure by an amount which increases with increasing inlet duct absolute pressure.

United States Patent Silvester Nov. 13, 1973 FUEL INJECTION SYSTEMS3,319,613 5/1967 Begley ct al 123/32 EA 3,543,739 12/1970 Mennesson....V 123/32 EA [75] Inventor" Bria Caro Leammgto" 3,596,640 8/1971Bloomfield 123/32 EA Spa, England [73] Assignee: Associated EngineeringLimited, Primary Examiner-Laurence Goodridge Leamington S a, w i k hiAssistant Examiner-Cort Flint England Att0rneyI-lolcombe, Wetherill &Brisebois d: [22] File Sept 30, 1971 [57] ABSTRACT [2]] Appl' 185,090This invention relates to a fuel injection system and to [30] ForeignApplication Priority Data 21 fuel pressure regulator therefor. A fuelinjection system, for injecting pressurised fuel into an inlet duct ormanifold of an engine includes a fuel-flow metering Sept. 30, GreatBlltall'l Orifice is fed the pressurised fuel and 521 US. Cl 123/139 AW,123/140 MP which is exposed its downstream Side to the [51] Int. Cl.F02m 39/00 Sure Obtaining in the inlet duct manifold, and a fuel 58Field of Search 123/119 R, 32 EA, Pressure regulator is arranged toregulate the fuel to a 23/32 AB, 139 w 140 Mp pressure which exceeds theinlet duct pressure by an amount which increases with increasing inletduct ab- [56] References Cited Solute Pressure- UNITED STATES PATENTSGroves 123/1 19 7R 7 A 5 95939 11 Pwrviesi e s,

FUEL INJECTION SYSTEMS This invention relates to a fuel injection systemand to a fuel pressure regulator therefor.

According to one aspect of the invention there is provided a fuelinjection system, for injecting pressurised fuel into an inlet duct ormanifold of an engine, including a fuel-flow metering orifice to be fedwith the pressurised fuel and to be exposed on its downstream side tothe pressure obtaining in the inlet duct, and including a fuel pressureregulator arranged to regulate the fuel to a pressure which exceeds theinlet duct pressure by an amount which increases with increasing inletduct absolute pressure.

Conveniently the supply of fuel to the orifice is periodicallyinterrupted for predetermined times to control the flow of fuel.

Suitably the interruption of fuel supply is effected by a solenoidoperated injector valve.

According to another aspect of the invention there is provided a fuelpressure regulator, for use in a fuel injection system of the typearranged to inject pressurised fuel into an air duct or manifold of anengine, including a member having an area subject to the pressure offuel to be regulated, the fuel pressure generating a force on the membertending to move it to open an aperture so as to reduce fuel pressure,and another area in the regulator exposed to the pressure of the air inthe duct, the said other area being connected to the member in a mannerwhich would generate a greater force on the member than the opposingforce generated on the member by the first-mentioned area if both areaswere subject to the same pressure. Preferably the two areas are directlyconnected but the said other area is greater than the first-mentionedarea.

The invention is described, by way of example only, with reference tothe accompanying drawing which is an axial section through oneembodiment of the invention.

In the drawing a valve, for regulating the pressure of liquid fuel fedto the injector in a fuel injection system ,of an internal combustionengine, has a body in which are formed fuel inlet and outlet passages11, 12, respectively. The passages 11, 12 are joined by a bore 13 whichterminates in a larger concentric bore 14 adjacent the outlet passage12. The junction of the bores 13, 14 is a shoulder having a sharp corner15.

A hollow cylindrical plunger 16 is an accurate sliding fit in the bore13 and is urged towards the blind end 17 of the bore 13 by a low ratepre-compressed helical spring 18.

The spring 18 reacts against a thimble 19 mounted on the end of anadjusting screw 20. The latter is screwed into an end cap 21 which isheld to the body 10 by a nut 22 to close the outlet end of the bores 13,14. The plunger 16 has a circumferential groove 23 formed with a sharpcorner 24 which aligns with the sharp corner when the plunger 16 is incontact with the blind end 17 of the body 10. The groove 23 communicateswith the inlet passage 11 by longitudinal grooves 25 formed in theplunger 16.

When pressurised fuel is admitted through the inlet passage 11 itproduces an axial force on the plunger 16 which moves it to the right inthe FIGURE to open an aperture between the sharp corners 15, 24. Due tothe low rate of the spring 18 the pressure of inlet fuel increases thisaperture until the fuel flowing therethrough has the desired regulatedinlet pressure.

Fuel having passed through the regulating aperture escapes through thelarger bore 14 and outlet passage 12.

The interior of the plunger 16 and the end space 28 of the bore 14adjacent the end cap 21 is vented to inlet manifold pressure through abore 26 in the adjusting screw 20 which is locked by a lock nut 27. Theplunger 16 is sealed to the body 10 by a rubber-like or other suitablediaphragm 29. The diaphragm 29 is held against an end face of the body10 by a spacer sleeve 40, which is trapped by a further rubber-likediaphragm 41 and the end cap 21. The diaphragm 29 is held against theright hand end face of the plunger 16 by a shouldered sleeve 42 screwedinto the plunger 16, and the further diaphragm 41 is sealed by ashouldered sleeve 30, screwed into the shouldered sleeve 42.

Downstream of the regulating aperture the plunger 16 has a reduceddiameter portion 31. Any backpressure obtaining in the outlet passage 12will act on the difference in area between the plunger 16 at the sharpshoulder 24 and at the reduced diameter portion 31 to produce forcetending to urge the plunger 16 towards the left in the FIGURE.Simultaneously the outlet back-pressure acts on the diaphragm 29 toproduce a force on the plunger 16 tending to move the latter to theright. By careful selection of the inner and outer diameters of thatpart of the diaphragm 29 exposed to the outlet back-pressure, it ispossible to equate the opposing forces on the plunger 16 due to theoutlet back-pressure. By this means the pressure regulating valve willadjust the pressure on its inlet passage 11 to a value which issubstantially independent of any variations in the pressure of the fuelpassing through the outlet passage 12.

The space 43 between the diaphragms 29 and 41 is connected by a passage44 and pipe 45 to a source of pressure which is sufficiently constant incomparison with the fuel and inlet manifold pressures. Such a source ofpressure may be a container having a high vacuum sealed within, or insome cases could be atmospheric pressure.

It will be apparent that the effective cross-sectional area of thediaphragm 29 is equal to the cross-sectional area of the sharp cornersl5 and 24. It will also be apparent that the effective cross-sectionalarea of the diaphragm 41 and the attached plunger 16 which is exposed tothe inlet manifold pressure is greater than the cross-sectional area ofthe sharp comer 15.

In operation, the pressure of fuel in the inlet 11 will move the plunger16 until the force on the plunger due to fuel pressure balances the netforce on the plunger due to other causes. The force due to the fuelequals the fuel pressure multiplied by the cross-sectional area of theshoulder 15. The net force due to other causes equals the force due tothe spring 18 (substantially constant) plus the pressure in the space 43multiplied by the difference in effective cross-sectional areas of thediaphragms 29, 41 (also substantially constant) plus the inlet manifoldpressure multiplied by the effective cross-sectional area of thediaphragm 41 and plunger 16.

Due to the effective cross-sectional area of the diaphragm 41 beinggreater than the cross-sectional area of the shoulder 15, it will beseen that the fuel pressure in the inlet 11 will always be above theinlet manifold absolute pressure and the fuel pressure will exceed theinlet manifold pressure by an amount which increases with increasinginlet manifold absolute pressure.

In this way the pressure difference across any fuel injector, fed fromthe inlet 11 and injecting into the inlet manifold, will increase withincreasing inlet manifold absolute pressure.

Instead of the diaphragms 29 or 41 any other suitable type ofaxially-free seal could be used such as the sleeve 42 having an enlargedleft-hand end and sliding in a corresponding bore in the body 10.

Furthermore, if preferred the areas subject to fuel pressure and inletmanifold pressure respectively could be of equal size but the areasubject to the inlet manifold pressure could be connected to the plunger16 by a force-multiplying lever or equivalent system.

I claim:

1. In a fuel pressure regulator for use in a fuel injection systemarranged to inject fuel into a duct in an engine, said regulatorcomprising,

means defining an aperture the degree of opening of which affects saidfuel pressure,

a member having a first area exposed to the pressure of the fuel to beregulated so that said fuel pressure generates a force onsaid memberuring it to open said aperture and thereby reduce said fuel pressure,

a surface in said regulator having a second area ex-- posed to thepressure of air in said duct and positioned to generate a force on saidmember in response to said air pressure urging said member to close saidaperture and thereby increase said fuel pressure,

the improvement according to which the surface having said second areatransmits to said movable member a force which is greater in proportionto the pressure exerted by said air on said second area than the forcegenerated by said fuel on said member in proportion to the fuel pressureto which said first area is exposed.

2. A fuel pressure regulator as claimed in claim 1, wherein said memberis a plunger including the first area subject to the fuel pressure to beregulated and said surface having the second area is a diaphragmconnected to said plunger and subjected to inlet duct pressure.

3. A fuel pressure regulator as claimed in claim 2, wherein said plungeroperates in a bore and a corner of a shoulder formed on the plungercooperates with a corner of said bore to define a fuel metering aperturebetween said corners, and a low rate spring tends to urge the plunger ina direction to close said aperture.

4. A fuel pressure regulator as claimed in claim 3, wherein a seconddiaphragm is connected to said plunger and is subjected to fuel outletpressure and the space between said two diaphragms is connected to asource of substantially constant pressure with respect to fuel pressureand inlet duct pressure, and further wherein the effectivecross-sectional area of said second diaphragm is equal to thecross-sectional area of said corners, and the effective cross-sectionalarea of said first diaphragm and of the plunger which is exposed toinlet duct pressure is greater than the crosssectional area of the sharpcorner on said bore.

5. A fuel pressure regulator as claimed in claim 1, wherein the twoareas are directly connected but the said second area is greater thanthe first area.

1. In a fuel pressure regulator for use in a fuel injection systemarranged to inject fuel into a duct in an engine, said regulatorcomprising, means defining an aperture the degree of opening of whichaffects said fuel pressure, a member having a first area exposed to thepressure of the fuel to be regulated so that said fuel pressuregenerates a force on said member uring it to open said aperture andthereby reduce said fuel pressure, a surface in said regulator having asecond area exposed to the pressure of air in said duct and positionedto generate a force on said member in response to said air pressureurging said member to close said aperture and thereby increase said fuelpressure, the improvement according to which the surface having saidsecond area transmits to said movable member a force which is greater inproportion to the pressure exerted by said air on said second area thanthe force generated by said fuel on said member in proportion to thefuel pressure to which said first area is exposed.
 2. A fuel pressureregulator as claimed in claim 1, wherein said member is a plungerincluding the first area subject to the fuel pressure to be regulatedand said surface having the second area is a diaphragm connected to saidplunger and subjected to inlet duct pressure.
 3. A fuel pressureregulator as claimed in claim 2, wherein said plunger operates in a boreand a corner of a shoulder formed on the plunger cooperates with acorner of said bore to define a fuel metering aperture between saidcorners, and a low rate spring tends to urge the plunger in a directionto close said aperture.
 4. A fuel pressure regulator as claimed in claim3, wherein a second diaphragm is connected to said plunger and issubjected to fuel outlet pressure and the space between said twodiaphragms is connected to a source of substantially constant pressurewith respect to fuel pressure and inlet duct pressure, and furtherwherein the effective cross-sectional area of said second diaphragm isequal to the cross-sectional area of said corners, and the effectivecross-sectional area of said first diaphragm and of the plunger which isexposed to inlet duct pressure is greater than the cross-sectional areaof the sharp corner on said bore.
 5. A fuel pressure regulator asclaimed in claim 1, wherein the two areas are directly connected but thesaid second area is greater than the first area.